Researchers analyzed data from 18 studies -- most conducted in Europe or North America -- and found that people with memory and thinking problems were 39 percent more likely to suffer a stroke than those with normal mental function.

When the team broadened its definition of mental decline (clinically called "cognitive impairment"), the connection to stroke got even stronger. The findings did not prove cause-and-effect, however.

"This risk increased to 64 percent when a broadly adopted definition of cognitive impairment was used," wrote a team led by Dr. Bruce Ovbiagele, chair of the neurology department at the Medical University of South Carolina.

"Given the projected substantial rise in the number of older people around the world, prevalence rates of cognitive impairment and stroke are expected to soar over the next several decades, especially in high-income countries," the researchers added.

Why is poor mental ability seemingly tied to increased stroke risk? Weakened mental ability probably doesn't cause a stroke, but Ovbiagele's team believes that circulatory issues -- such as blockages of blood vessels in the brain, narrowing of the arteries, and inflammation -- are all associated with a higher risk of stroke.

A decline in thinking and memory skills may therefore be "a possible early clinical manifestation" of this type of trouble in the brain, they suggested.

That means that better management of heart disease and circulatory issues "can be instituted to potentially prevent future stroke events and to avoid further deterioration of [brain] health," the researchers reported Aug. 25 in the CMAJ (Canadian Medical Association Journal).

The findings echo those of another recent study, published earlier this month in the journal Stroke.

That research was led by Kumar Rajan, assistant professor of internal medicine at Rush University Medical Center in Chicago. His team tracked more than 7,200 Americans over 65 years of age who were given tests every three years to evaluate their short- and long-term memory, attention, awareness and other mental functions.

Those with lower test scores were 61 percent more likely to suffer a stroke than those with higher scores, the researchers found.